Several specific approaches are defined to elucidate participation of the host's immunologic responses to oral microbial products in human periodontal diseases. A. To determine the relationship of serum and local antibodies to the oral microbiota in various periodontal patients. B. To measure phagocyte function in periodontal diseases. C. To assess lymphocyte function in periodontal diseases, with an emphasis on control mechanisms and mechanisms of immunopathology.